Method for correcting downstream deflection in gas turbine nozzles
a gas turbine and downstream deflection technology, applied in the field of gas turbines, can solve problems such as deformation of stationary turbine nozzles
Inactive Publication Date: 2014-11-18
DRESSER RAND CO
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Benefits of technology
The patent describes a method and apparatus for refurbishing a gas turbine nozzle by heating and reshaping it with a calculated amount of force. The refurbishing process includes mounting the nozzle in a fixture, using a hydraulic jack to exert an upward force on the inner shroud, and monitoring the temperature using thermocouples. The technical effect of the patent text is to provide a way to restore the shape and performance of gas turbine nozzles that have been worn or damaged during use.
Problems solved by technology
One problem with gas turbines is that the gas loading on the nozzles and the high temperatures in the turbine, eventually cause the stationary turbine nozzles to deform.
This is a particular problem with turbines where the nozzles are made of cobalt-based superalloys and use a cantilevered design.
Method used
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[0020]In a cantilevered gas turbine design, a ring 100, as illustrated in a radial view in FIG. 1, is composed of a plurality of circumferentially spaced apart stationary nozzles 110, each of which includes vanes supported between radially inner and outer bands or shrouds. Each nozzle 110 is typically an arcuate segment with two or more vanes joined between the inner and outer shrouds, as shown in more detail in FIG. 2. Each vane is an airfoil, and the vanes are typically cast with the inner and outer shrouds to form the nozzle.
[0021]Each nozzle 110 is cantilevered from the outer shroud, using hook to hold the nozzle in place. As the stationary nozzles 110 deform in a downstream direction, commonly referred to as downstream deflection (DSD), the nozzle 110 provides reduced axial clearances and radial seal clearances are compromised. As a consequence of the compromised clearances caused by the DSD, sealing effectiveness is reduced, which can result in high wheel space temperatures.
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Abstract
A gas turbine nozzle can be refurbished to reduce downstream deflection. The outer shroud of the gas turbine nozzle is held in a fixture, and then the nozzle is heated. The heated nozzle is then reshaped by a force exerted upon the inner shroud of the gas turbine, reducing the downstream deflection of the nozzle. After the deformation of the nozzle, an aft hook of the nozzle that has been adjusted by previous refurbishment efforts can be rebuilt to remove the previous adjustments.
Description
TECHNICAL FIELD[0001]The present invention relates to the field of gas turbines, and in particular to a technique for refurbishing gas turbine nozzles.BACKGROUND ART[0002]In a gas turbine, gas is typically produced by the combustion of fuel. The gas is then passed over a collection of stationary nozzles, which discharge jets of gas against the blades of a turbine rotor, forcing the rotor to rotate. The rotation of the rotor drives the external load of the turbine, such as an electrical generator.[0003]One problem with gas turbines is that the gas loading on the nozzles and the high temperatures in the turbine, eventually cause the stationary turbine nozzles to deform. This is a particular problem with turbines where the nozzles are made of cobalt-based superalloys and use a cantilevered design.SUMMARY OF INVENTION[0004]In one embodiment, a method of refurbishing a gas turbine nozzle comprises mounting the gas turbine nozzle in a fixture, heating the gas turbine nozzle to a predeterm...
Claims
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IPC IPC(8): B23P6/00B21D3/00
CPCB21D3/00B23P6/002Y10T29/37Y10T29/49318B21D3/16
Inventor GAUL, GREGORY, R.
Owner DRESSER RAND CO